Process for low contrast development

ABSTRACT

WHEREIN R1, R2, R3 AND R4 EACH REPRESENTS A HYDROGEN ATOM, AN ALKYL GROUP, A HYDROXYL GROUP, OR AN ALKENYL GROUP.   1-R1,2-R2,4-R3-IMIDAZOLE   WHEREIN R REPRESENTS AN ALKYL GROUP, AN ARALKYL GROUP OR AN ARYL GROUP, AND R&#39;&#39; AND R&#34; EACH REPRESENTS A HYDROGEN ATOM OR AN ALKYL GROUP, WHEREIN SAID R&#39;&#39; AND R&#34; MAY FORM A CONDENSED RING AND WHEREIN SAID CONDENSED RING MAY BE SUBSTITUTED BY AN ALKYL GROUP; AND AN IMIDAZOLE COMPOUND REPRESENTED BY THE FOLLOWING FORMULA:   2-(R-S-CH2-CO-NH-),4-R&#34;,5-R-THIAZOLE   A DEVELOPING PROCESS FOR SILVER HALIDE PHOTOGRAPHIC LIGHT-SENSITIVE MATERIALS WHICH COMPRISES DEVELOPING THE PHOTOGRAPHIC MATERIALS IN THE PRESENCE OF A THIAZOLE COMPOUND REPRESENTED BY THE FOLLOWING FORMULA:

United States Patent Int. Cl. (30361/34, /30

US. Cl. 96-66.3 11 Claims ABSTRACT OF THE DISCLOSURE A developing process for silver halide photographic light-sensitive materials which comprises developing the photographic materials in the presence of a thiazole compound represented by the following formula:

wherein R represents an alkyl group, an aralkyl group or an aryl group, and R and R" each represents a hydrogen atom or an alkyl group, wherein said R' and R" may form a condensed ring and wherein said condensed ring may be substituted by an alkyl group; and an imidazole compound represented by the following formula:

wherein R R R and R each represents a hydrogen atom, an alkyl group, a hydroxyl group, or an alkenyl group.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to a process of low contrast development and more particularly, it relates to a process of low contrast development for silver halide photographic light-sensitive materials.

Description of the prior art It is an important subject in the development of silver halide photographic light-sensitive materials to control the gamma of the silver images obtained. It is also important for some kinds of materials, especially in microfilming, to obtain a fine grained developed image. For this purpose, various fine grain developing solutions are known. For instance, some are disclosed in the specifications of US. Pats. Nos. 2,164,280, 2,113,312; 2,311,428 and 2,840,471 and British Pat. No. 723,286. However, because the images obtained by processing general photographic materials in the fine grain developing solutions taught by the above-mentioned patents often do not have suificient resolving power and granularity, such known fine grain developing solutions are insufficient for obtaining images having high resolving power and excellent granularity.

As light-sensitive materials having excellent resolving power and granularity, microfilms are commercially avail able but since such materials are among the so-called high contrast films having high gamma characteristics, they are unsuitable for recording tonal scenery although they are excellent in resolving power and granularity.

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To obtain so-called soft-tone images having low gamma characteristics and high speed, without any loss of granularity or resolving power on a fine grain, low speed, high contrast photographic film by a particular way of development, would be quite useful and would provide a wide range of application. Developing processes for satisfying such purposes have hitherto been investigated and one of the improvements is disclosed in the specification of French Pat. No. 1,495,935. In the improvement shown in the French Pat., the high contrast photographic film of the above-mentioned type is softened by develop ing the film after pre-treating it in an aqueous solution of a noble metal salt. Another improvement is also disclosed in the specification of Japanese patent publication No. 14,5 10/ 69, which discloses the reduction of the gamma of high contrast photographic film by developing it in an ordinary low contrast developing solution and then fixing the film in a fixing solution having incorporated therein an oxidizing agent. In this process, the fixation and bleaching take place at the same time.

However, the invention disclosed in the specification of the above-mentioned French Patent has such faults that an expensive noble salt must be used and further the process becomes complicated because of the requirement of the additional bath. On the other hand, the process disclosed in the specification of the Japanese patent publication mentioned above has such faults that the period of time for fixing must be strictly controlled because of the addition of an oxidant to the fixing solution, the life of the fixing solution is also reduced and it is difficult to handle since the fixing solution contains an oxidizing agent.

As mentioned above, it is quite diflicult to soften high contrast photographic films by the device of a developing process only.

A developing solution containing l-phenyl-3-pyrazoli done developing agent can soften high contrast photographic film but it is accompanied by low sensitivity and is very easily exhausted by processing a small quantity of films. On the other hand, a developing solution containing N-methyl-p-aminophenol developing agent may have a high sensitivity but it is not effective for obtaining a soft-tone image. A developing solution containing a suitable amount of l-phenyl-3-pyrazolidone and N-methylp-aminophenol may have a high sensitivity and can give a considerably soft-tone image but is easily exhausted. Moreover, a developing solution containing a suitable amount of 1-phenyl-3-pyrazolidone, N-methyl-p-aminophenol and hydroquinone developing agent may have a high sensitivity and is not easily exhausted but it is impossible to obtain good soft-tone images by using such a developing solution. Thus, only by changing or selecting a particular developing agent, it is almost impossible to obtain a developing solution giving a high sensitivity, having a good resistance to exhaustion and which is capable of producing soft-tone images.

An object of this invention is to provide a process of enlarging the exposure latitude by low contrast development and varying widely the characteristics of a silver halide hard-tone light-sensitive material without lowering the granularity and resolving power of the light-sensitive material.

SUMMARY OF THE INVENTION The above-mentioned object of this invention is achieved by development in the presence of the thiazole derivative represented by General Formula I,

Formula I wherein R represents an alkyl group, an aralkyl group such as a benzyl group or an aryl group, and R and R" each represents a hydrogen atom or an alkyl group; wherein said R and R" may form a condensed ring and further said condensed ring may be substituted with an alkyl group;

together with the imidazole derivative represented by General Formula II,

Formula II wherein R R R and R each represents a hydrogen atom, an alkyl group, a hydroxyalkyl group or an alkenyl group.

In the above two formulae, the alkyl group described preferably contains from 1 to 5 carbon atoms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the thiazole derivatives represented by General Formula I are as follows:

Compound I-1 S H: NHO OCHzS CH:

Compound I-2 S H: NHO OCH: S 02115 Compound 1-3- H NH 0 onis Compound 1-4 NHCOCH2SCH2 Compound 1-5 NH0 0 CHZS C 11 Examples of the imidazole derivatives represented by General Formula II are as follows:

Compound 1-6 Compound 1-7 4 11-1 3-4-( Z-hydroxyethyl -5-methylimidazole, II14-1-allyl-2-methylimidazole, IL-15-1-vinyl2-methylimidazole, etc.

The thiazole derivatives represented by General Formula I give less loss of speed and more remarkable softening effects as compared with other conventional organic antifoggants. However, the low contrast development by these thiazole derivatives is still accompanied by some loss of speed. An improvement of low contrast development with an improved speed will, therefore, be advantageous for many fields of application. For increasing the speed, the use of a development accelerator such as an amine compound or a polyethylene oxide is known but the use of such an accelerator is not preferable since the com pound tends to increase the contrast of the processed image.

The inventors have previously discovered that the imidazole derivatives represented by the above-mentioned General Formula'II show excellent development accelerating effects (Japanese patent application No. 5,126/ 1969). That is to say, when the imidazole derivative represented by General Formula II is incorporated in a developing solution containing 1 phenyl-3-pyrazolidone and hydroquinone or N-methyl-p-aminophenol and hydroquinone, the speed is increased, the developing period is shortened, and the gamma is increased to some extent.

However, the inventors have further discovered that by adding the imidazole derivative to the developing solution containing the thiazole derivative, the speed is in creased and the contrast is reduced simultaneously. Thus, by these findings of fact, high contrast, comparatively low speed silver halide photographic materials may be realized by conducting the low contrast development with a high speed, keeping high resolving power and good granularity. Furthermore, by using a silver halide negative lightsensitive material having a comparatively high speed, a wide exposure range developing process becomes possible.

As the developing solution used for the softening development by using the above-mentioned compounds in this invention, there is used an aqueous solution containing at least one developing agent such as hydroqinone, 1-phenyl-3-pyrazolidone, N-methyl-p-aminophenol, and the like. The aqueous solution usually contains an anti oxidant such as sodium sulfite, ascorbic acid, etc; a pH- controlling agent such as boric acid, borax, sodium hydroxide, sodium carbonate, trisodium ortho-phosphate, etc.; a salt such as sodium sulfate, etc., and a butter agent. For further effecting the softening eifect, potassium bromide or potassium iodide may be added to the developing solution together with the above additives. Moreover, for reducing the formation of fog, an organic antifoggant may also be added to the developing solution. Still further, an aldehyde such as formalin, glutaraldehyde etc., with an organic solvent such as triethylene glycol, hexylene glycol, etc., may be used.

The concentration of the aforesaid compounds of this invention depends upon the composition of the developing solution used, the developing temperature, and the nature of the light-sensitive material to be processed but generally, the thiazole derivative is used in a range of from 1 mg. to 10 g. per liter of the developing solution and the irnidazole derivative is used in a range of from 10 mg. to g. per liter of the developing solution.

The compounds of this invention are elfective not only in the case where they are incorporated in a developing solution but also in the case where they are incorporated in the photographic emulsion layer of a light-sensitive material to be processed. Thus, although the above explanation describes adding the compounds to a developing solution, the use of such compounds is not limited to only this embodiment.

The following examples are intended to further illustrate the present invention, without being limited in nature.

EXAMPLE 1 A microfilm prepared by coating a fine grain silver chlorobromide gelatin emulsion on a support was exposed by means of a sensitometer and developed by one of the following three kinds of developing solutions A, B and C.

DEVELOPING SOLUTION A G. N-methyl-p-aminophenol sulfate 1.0 Sodium sulfite 75 Hydroquinone 9.0 Sodium carbonate mono-hydrate 30 Potassium bromide 5.0 Water to make 1 liter.

DEVELOPING SOLUTION B G, N-methyl-p-aminophenol sulfate 0.5 Sodium sulfite 10 Nabox 2.0 Water to make 1 liter.

DEVELOPING SOLUTION C G. l-phenyl-3-pyrazolidone 4.0 N-rnethyl-p-aminophenol sulfate 1.0 Sodium sulfite 100 Sodium carbonate mono-hydrate 30 Potassium bromide 5.0 Compound I 50 Compound II-3 2.0 Water to make 1 liter.

Developing solution A is an ordinary high contrast developing solution, developing solution B is a known soft-tone developing solution, and developing solution C is the low contrast developing solution of this invention.

The photographic properties of the images thus obtained by processing with the above three kinds of developing solutions are shown in the following table.

Photographic characteristics Fog Gamma Developing solution:

From the above results, it will be understood that only developing solution C has a particularly powerful effect of lowering gamma.

EXAMPLE 2 A microfilm prepared by coating a fine grain silver chlorobromide gelatin emulsion on a support was exposed by means of a sensitometer and then developed in developing solution D having the composition shown below at 27 C. For the sake of comparison, the same development was conducted by using developing solution F having the same composition except that Compound II-3 was omitted or solution B having the same composition except that Compound I-5 and Compound II-3 were omitted.

DEVELOPING SOLUTION D N-methyl-p-aminophenol sulfate g 2.0 l-phenyl-3-pyrazolidone g 8.0 Hydroquinone g 1.0 Sodium sulfite g 100 Potassium bromide g 5.0 Sodium carbonate mono-hydrate g 50 Triethylene glycol ml 100 Compound I-S mg 100 Compound II-3 g 4.0 2,4-dimercapto-1,3,4-thiadiazole mg 40 Water to make 1 liter.

The photographic properties of the images obtained by the developing processings are shown in the following table.

Photographic characteristics Gamma Fog Sensitivity 1 Developing solution:

l The value of sensitivity is shown by a logarithmic sensitivity when the sensitivity obatined by processing with control developing solution E was assumed to be 1.00.

As is shown by the above results, a higher sensitivity and lower gamma were obtained using developing solution 'D containing both compound I5 and compound II-3 than the case of using the developing solution containing only compound I-5.

EXAMPLE 3 Photographic characteristics Fog Sensitivity l Gamma Developing solution:

l The value of the sensitivity was shown by a logarithmic sensitivity when the sensitivity obtained by using developing solution E in example 2 was assumed to be 1.00.

EXAMPLE 4 A microfilm prepared by coating a fine grain silver chlorobromide gelatin emulsion onto a support was exposed by means of a sensitometer and then developed in developing solution I, having the same composition as developing solution D except that 4.0 g. of compound II-l was used instead of the compound 11-3; developing solution I having the same composition as developing solution D except that 4.0 g. of compound II2 was used instead of the compound II-3; developing solution K having the same composition as developing solution D except that 4.0 g. of compound II6 was used instead of compound II3; or developing solution L having the same composition as developing solution D except that 4.0 g. of compound II-7 was used instead of compound 'II-3; all at 27 C.

The photographic properties of the images obtained are shown in the following table.

Photographic characteristics Gamma v, The value of the sensitivity was shown by the logarithmic sensitivity when the sensitivity obtained by using developing solution E in example 2 was assumed to be 1.00.

We claim: 1. A developing process for silver halide photographic light-sensitive materials which comprises developing the exposed photographic materials in the presence of a thiazole compound represented by the following formula:

F R: R; l

wherein R R R and R each represents a hydrogen atom, an alkyl group, a hydroxyl group, or an alkenyl group.

2. The process according to claim 1 wherein said thiazole compound and said imidazole compound are incorporated in a developing solution.

3. The process according to claim 1 wherein said thiazole compound and said imidazole compound are incorporated in a photographic emulsion layer of a silver halide photographic material.

4. The process according to claim 2 wherein the amount of said thiazole compound added to the developing solution is from 1 mg. to 10 g. per liter of said solution.

5. The process according to claim 2 wherein the amount of said imidazole compound added to the developing solution is from 10 mg. to 100 g. per liter of the solution.

6. The process according to claim 2 wherein said developing solution contains as the developing agent at least one of the developers l-phenyl-3-pyrazolidone and N- methyl-p-amino-phenol sulfate.

7. The process according to claim 2 wherein said developing solution contains a compound represented by the formula,

and 2-methyl-imidazole.

8. The process according to claim 1 wherein said alkyl group contains from 1 to 5 carbon atoms.

9. Silver halide photographic light-sensitive materials produced by the process of claim 1.

10. The process according to claim 1 wherein said thiazole compound is selected from the group consisting of Compound I-l S NHC OCHrSCHI S NHCOCH:SC2H

Compound I-3 S UMGOGW Compound I-4 S O NHC OCHzS OH:

11. The process according to claim 1 wherein said imidazole compound is selected from the group consisting of imidazole, l-methylimidazole, Z-methylimidazole, 4- methylimidazole, Z-ethyli-midazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazo1e, 2-amylimidazole, l-isoamyl-Z- methylimidazole, 4,5-dimethylimidaz0le, 2,4,5-trimethylimidazole, 4-hydroxymethyl-S-methylimidazole, 4-(2-hydroxyethyl)-5-methylimidazole, 1-al1yl-2-methylimidazole, and 1-vinyl-2rnethylimidazole.

Compound I-2 Compound I-5 Compound I-6 and Compound I-7 References Cited UNITED STATES PATENTS 2,657,135 10/1953 Lowe 9652 2,657,136 10/1953 Knott 9652 3,023,103 2/1962 Dersch 96107 3,147,118 9/ 1964 Dersch 96109 3,271,154 9/1966 Dersch 96109 FOREIGN PATENTS 699,858 11/1953 Great Britain 96109 708,065 4/1954 Great Britain 96109 NORMAN G. TORGHIN, Primary Examiner M. F. KELLEY, Assistant Examiner US. Cl. X.R. 9666 R, 66.5, 109 

